Medical instrument electrically energized using drive cables

ABSTRACT

An electrically energized medical instrument uses one or more drive cables to both actuate mechanical components of a wrist mechanism or an effector and to electrically energize the effector. Electrical isolation can be achieved using an insulating main tube through which drive cables extend from a backend mechanism to the effector, an insulating end cover that leaves only the desired portions of the effector exposed, and one or more seals to prevent electrically conductive liquid from entering the main tube. Component count and cost may be further reduced using a pair of pulleys that are shared by four drive cables.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation U.S. patent application Ser.No. 15/855,561, filed Dec. 27, 2017, which is a continuation of U.S.patent application Ser. No. 14/933,875, filed Nov. 5, 2015, which is adivisional of U.S. patent application Ser. No. 12/173,938, filed Jul.16, 2008 (now U.S. Pat. No. 9,204,923), which is related to andincorporates by reference U.S. patent application Ser. No. 12/173,934,entitled “Four-Cable Wrist with Solid Surface Cable Channels,” each ofwhich is incorporated herein by reference in its entirety.

BACKGROUND

Minimally invasive medical procedures generally employ small diameterinstruments that can be inserted directly or through a cannula in asmall incision or natural orifice of a patient. Producing small diametermedical instruments that implement the clinically desired functions forminimally invasive procedures can be challenging. For example, manyinstruments require a small-diameter wrist mechanism that is able toposition and manipulate an end effector at the distal end of theinstrument. Such wrist mechanisms commonly employ two cables perrotation axis available in the wrist, so that a wrist mechanismproviding pitch, yaw, and grip control commonly uses six cables. All ofthe cables must be routed through the wrist mechanism and back through asmall-diameter tube to a transmission, sometimes referred to herein as abackend mechanism. The backend mechanism moves the drive cables asneeded to operate the wrist mechanism. Further, some medical instrumentshave end effectors that require electrical energy, for example, forclinical functions such as desiccation, hemostasis, cutting, dissection,fulguration, incisions, tissue destruction, cauterizing, and vesselsealing. Accordingly, one or more conductors must be routed to theportion of an end effector to be energized, while other portions of theinstrument must be insulated from the electrical energy to avoidunintended burning of the patient or a user of the instrument. Fittingall the components of the wrist mechanism, drive cables, and conductivewires into a small diameter, for example, less than about 10 mm, can bedifficult.

Minimally invasive medical instruments with lower part counts aredesired to facilitate miniaturization of the instrument and to reduceinstrument costs.

SUMMARY

In accordance with an aspect of the invention, an electrically energizedmedical instrument uses one or more drive cables both to actuatemechanical components of a wrist mechanism or an end effector and toelectrically energize the end effector. Electrical isolation can beachieved using an insulating main tube through which drive cables extendfrom a backend mechanism to an end effector, an insulating end coverthat leaves only the desired portions of the end effector exposed, andone or more seals to prevent electrically conductive liquid fromentering the main tube. A reduction in the number of components achievedby some embodiments of the invention can result in a cost savings in areusable instrument or permit creation of a single-use instrument thatis cost competitive with reusable instruments on a per use basis.

One specific embodiment of the invention is a medical instrumentincluding a main tube, an end effector, a cable, and a backendmechanism. The end effector is attached to a distal end of the main tubeand contains an electrically conductive component such as a scissorsblade. The cable extends the length of the main tube and is coupled tothe end effector so that actuation of the end effector involves movementof the cable. The cable is also electrically conductive. The backendmechanism is coupled to a proximal end of the main tube and includes amechanical system and an electrical system. The mechanical system iscoupled to the cable and is operable to move the cable for the actuationof the end effector. The electrical system is connected to the cable forapplication of an electrical signal that energizes the electricallyconductive component of the end effector. The energized end effector canthen be used for a clinical function such as destroying or cauterizingtissue.

Another embodiment of the invention is a method for operating a medicalinstrument. The method includes: actuating an end effector on a distalend of a main tube through movement of one or more cables that areattached to the end effector; and electrically energizing the endeffector by applying an electrical signal that one or more of the cablesconducts through the main tube to the end effector.

Yet another embodiment of the invention is a medical instrumentincluding a clevis, a pair of pulleys, a pair of jaws, and four drivecables. The clevis and the pulleys are rotatably mounted on a first pin.The jaws are rotatably mounted on a second pin that is in the clevis. Afirst and a second of the cables attach to one jaw and respectively rideon the first and second pulleys when the clevis is in a first position.A third and a fourth of the cables attach to the other jaw and also rideon the first and second pulleys, respectively, when the clevis is in thefirst position. Having four cables share two pulleys decreases the partcount and the cost of the instrument. The pulleys reduce cable frictionbecause for many motions of the instrument (e.g., change of the pitchangle or closing/opening of the jaws) the rotation of each pulleymatches the movement of both cables that ride on the pulley. For othermotions of the instrument, a cable may slide or slip on a pulley whenthe motions of both cables cannot simultaneously be matched to therotation of the pulley. However, the pulley will generally rotate withwhichever of the associated cables exerts greater force on the pulley,e.g., has the larger wrap angle and/or tension, so that the total cablefriction can be reduced even when a cable is required to slide againstthe surface of a pulley.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a medical instrument that operates as an energized endeffector in accordance with an embodiment of the invention.

FIGS. 2A and 2B respectively show closed and open configurations ofscissors in an end effector suitable for the medical instrument of FIG.1.

FIGS. 3A and 3C show partial cutaway views of the end effector of FIGS.2A and 2B.

FIG. 3B shows an exploded view of scissors in accordance with anembodiment of the invention.

FIGS. 4A, 4B, and 4C show a wrist mechanism in accordance with anembodiment of the invention using a pair of devises and four drivecables that slide on guide surfaces integrated into the devises.

FIGS. 5A and 5B illustrate jaws with cables attached using high frictionpaths in accordance with alternative embodiments of the invention.

FIG. 6A illustrates the movements of four drive cables that producechanges in the pitch, yaw, and grip of a wrist mechanism in accordancewith an embodiment of the present invention.

FIG. 6B shows a perspective view illustrating pivot axes of the wristmechanism of FIGS. 4A, 4B, and 4C when operated using the cablemovements of FIG. 6A.

FIG. 7 shows an embodiment of a seal suitable for use in a medicalinstrument in accordance with an embodiment of the invention.

FIGS. 8A and 8B, respectively, show an exploded view and across-sectional view of a backend mechanism in accordance with anembodiment of the invention using gears and levers to move drive cablesand an electrical connection to energize at least one of the drivecables.

FIG. 9A shows a backend mechanism in accordance with an embodiment ofthe invention using pulleys, capstans, and gears to move drive cablesand an electrical connection to energize at least one of the drivecables.

FIG. 9B shows the backend mechanism of FIG. 9A in accordance with anembodiment of the invention using a keeper to keep drive cables in theirdesired positions and provide electrical connections to the drivecables.

Use of the same reference symbols in different figures indicates similaror identical items.

DETAILED DESCRIPTION

In accordance with an aspect of the invention, a robotically actuated,electrically energized instrument can use one or more actuating or drivecables for electrical power. One specific embodiment of the invention isa low cost, wristed, electrically energized, scissor instrument that canbe actuated using a robotic control system such as the da Vinci systemavailable from Intuitive Surgical, Inc. Using drive cables forelectrical energy can reduce the number of component parts, which canresult in cost reduction and can facilitate miniaturization ofinstruments for minimally invasive medical procedures. An additionalreduction in the part count and costs can be achieved by routingmultiple cables around the same pulley in the wrist of the instrument.

FIG. 1 shows a configuration for a medical instrument 100 in accordancewith an exemplary embodiment of the invention. Medical instrument 100includes an end effector 200 at a distal end of a main tube 110 thatextends from a transmission or backend mechanism 120. During a minimallyinvasive medical procedure, end effector 200 and the distal end of maintube 110 can be directly inserted or inserted through a cannula or otherguide that may be inserted through a small incision or a natural orificeof a patient undergoing the medical procedure. Accordingly, the diameterof end effector 200 and main tube 110 and the length of main tube 110may be selected according to the size of the cannula with which theinstrument will be used. In an exemplary embodiment, end effector 200and main tube 110 are about 5 mm or about 8 mm in diameter to match thesizes of some existing cannula systems, and the length of main tube 110can be about 460 mm.

Main tube 110 is hollow to contain drive cables that run from backendmechanism 120 to end effector 200. In accordance with an aspect of thecurrent invention, main tube 110 is made of an electrically insulatingmaterial such as a plastic or polymer material to isolate the drivecables, which may be electrically energized, from the surroundingenvironment. Main tube 110 may be rigid or flexible. A flexible maintube 100 would be used, for example, for insertion through an endoscopeor other guide or cannula that follows a natural lumen or otherwisecurved path. However, many common types of minimally invasive medicalprocedures such as laparoscopic surgery employ straight cannulas forinsertion and removal of instruments, permitting use of a rigid maintube 110. A rigid main tube 110 can provide a solid base for use of endeffector 200 during a medical procedure. A rigid/straight main tube 110also permits portions of drive cables extending through main tube 110 tobe structures such as rods or tubes (e.g., hypotubes) that may providebetter immunity to stretching or be less expensive.

Backend mechanism 120 can contain an electrical system for energizingend effector 200 and a mechanical system that acts as a transmission andprovides a mechanical interface between the drive cables extendingthrough main tube 110 and a control system (not shown). In an exemplaryembodiment of the invention, the control system is the da Vinci systemavailable from Intuitive Surgical, Inc. The control system containsdrive motors under the control of a processing system, software, andinput from a user interface. In general, backend mechanism 120 is shapedto be fitted in a docking port or elsewhere onto the control system sothat motor driven axes of the control system can operate end effector200 to produce desired movements, e.g., changes of the pitch, yaw, andgrip of end effector 200.

FIG. 2A shows an embodiment in which end effector 200 contains scissors240. Scissors 240 can be electrically energized with an AC signal. Forexample, the AC signals may use a voltage of 100 volts up to 10,000volts or more and a frequency above 100 kHz and typically between about350 kHz and 4 MHz. Such AC signals are known in the art for performingclinical functions such as desiccation, hemostasis, cutting, dissection,fulguration, incisions, tissue destruction, cauterizing, and vesselsealing without shocking a patient. An insulating cover 260 shown inFIG. 2A covers most of end effector 200 so that only the blades ofscissors 240 are exposed. During a medical procedure, scissors 240 canbe energized with the high voltage AC signal when a contact pad on thepatient is grounded or energized with an opposite polarity AC signal.Since only the blades of scissors 240 expose electricity to the patient,an electrical current flows only from the blades through tissue adjacentto the blades when scissors 240 are electrically energized. Theconcentration of electrical current can be used to destroy tissue and/orcauterize tissue during cutting with or other use of scissors 240. Thecontact pad on the patient's body is designed to make a wide areaelectrical connection to spread the current sufficiently to avoid tissuedamage or burning at the body contact or anywhere away from the bladesof scissors 240.

Cover 260 can be made of rubber, silicone, or another flexibleinsulating material and is attached to main tube 110 by a compressionclip 262 or alternatively by an elastic ring, a heat shrinkable ring, arigid ring, or other retaining structure. With a rigid ring, thematerial of cover 260 under the rigid ring can provide the elasticityneeded for assembly of the instrument. Some suitable materials for clip262 include stainless steel, plastic and nitinol.

FIG. 2A shows the blades of scissors 240 in the closed position, but awrist mechanism hidden by cover 260 can open scissors 240 and change theposition and orientation of scissors 240 during a medical procedure.FIG. 2B shows end effector 200 with scissors 240 in an openconfiguration and with cover 260 removed. Scissors 240 include blades242 and 244 that are pivotally mounted on a distal clevis 230. Blades242 and 244 are conductive and can be stamped metal blades. Distalclevis 230 is pivotally mounted on a proximal clevis 220, which isattached to the distal end of main tube 110.

Drive cables are connected to end effector 200 and are used to rotateblades 242 and 244 to change the yaw and grip of end effector 200 and torotate distal clevis 230 to change the pitch of end effector 200. In oneconfiguration, end effector 200 has only four drive cables that thebackend mechanism uses to control the pitch, yaw, and grip motions. Lowfriction interfaces can be used throughout the instrument to minimizeforce transmission losses that might otherwise lead to increased cablestretch. In particular, low friction interfaces can be created betweenthe drive cables and the guiding surfaces of proximal and distal devises220 and 230. Alternatively, pulleys can be provided at the highestfriction locations such as where the drive cables apply torque forrotation of distal clevis 230 about a pin in proximal clevis 220. Thedrive cables can also be swaged to provide smooth, low friction motion.Embodiments of the invention can also be implemented in systemsemploying more than four drive cables.

FIGS. 3A and 3B respectively show a partial cut away view of endeffector 200 and an exploded view of scissors 240 to better illustratethe operation of an embodiment of the invention using a four-cable wristmechanism. End effector 200 includes proximal clevis 220, distal clevis230, and scissors 240 as described above. Drive cables 251, 252, 253,and 254 are attached to scissors 240. More specifically, each blade 242or 244 as shown in FIG. 3B has a cap 241 or 243 that locks into blade242 or 244. Caps 241 and 243 slip onto pin 235 and have a notch thattraps a crimp 255 or 256. Alternatively, each cap 241 or 243 can bepermanently attached to the corresponding blade 242 or 244 (e.g., byswaging). Caps 241 and 243 can be metal, plastic, or other material thatprovides the desired strength and cost. Crimp 255 is attached to a cableloop having ends that extend back as cables 251 and 252, and crimp 256is attached to a cable loop having ends that extend back as cables 253and 254. When assembled into distal clevis 220, caps 241 and 243 holdcrimps 255 and 256 in respective notches, so that cables 251 and 252 areattached to blade 242 and cables 253 and 254 are attached to blade 244.

Cables 251, 252, 253, and 254 are made of a conductive material such asstranded metal cable or metal hypotubes, and may be an assembly withportions made of different materials. For example, portions of cables251, 252, 253, and 254 in the wrist mechanism can be made of strandedmetal cable for flexibility and may be swaged to provide smoother cablesurfaces and reduce friction. Portions of cables 251, 252, 253, and 254extending through main tube 110 may be hypotubes. An electricallyinsulating coating is not required on any of cables 251, 252, 253, or254 although one or more of cables 251, 252, 253, or 254 can be used toconduct an electrical signal from the backend mechanism to end effector240.

Cables 251, 252, 253, and 254 ride on pulleys 221 and 222, and fromthere extend back through main tube 110 to a backend mechanism (e.g.,backend mechanism 120 of FIG. 1). In the illustrated embodiment cables251 and 253 ride on pulley 221, and cables 252 and 254 ride on pulley222. A pin 225 in proximal clevis 220 provides an axel for pulleys 221and 222. Pin 225 also attaches distal clevis 230 to proximal clevis 220but allows distal clevis 230 to rotate about a pivot axis sometimesreferred to herein as the pitch axis. Pulleys 221 and 222 define aradius about pin 225 at which cables 251 and 252 act when rotatingdistal clevis 230 about pin 225, i.e., about the pitch axis.

When changing the pitch angle of end effector 200, the backend mechanismapplies a higher tension to one pair of cables 253 and 254 or 251 and252, and pulleys 221 and 222 and the distal clevis 230 rotate in adirection depending on which pair of cables 253 and 254 or 251 and 252has higher tension. The low tension pair of cables 251 and 252 or 253and 254 pay out at the same rate that the high tension cables are pulledin and therefore also rotate with pulleys 221 and 222. There is norelative sliding or slipping of cables 251, 252, 253, and 254 on pulleys221 and 222 when the pitch of end effector 200 is changed. Rotation ofpulleys 221 and 222 about pivot pin 225 results in lower cable frictionthan if cable 251, 252, 253, and 254 were sliding over an integralsliding surface in distal clevis 230.

A pin 235 in distal clevis 230 is perpendicular to pin 225 and defines apivot axis, sometimes referred to as the yaw axis or grip axis, forscissors 240 as a whole or blades 242 and 244 individually. The yaw axisand the grip axis coincide in end effector 200. The term grip is usedherein in a general sense since the action of blades 242 and 244 isgenerally to cut as blades 242 and 244 close or grip.

Opening or closing the grip of blades 242 and 244 without changing theyaw angle of end effector 200 requires high tension on cables that areon opposite sides of distal clevis 230. For example, to close jaws 242and 244, high tension is applied to cables 251 and 254. Equal lengths ofcables 251 and 254 are pulled in as the same length of cables 252 and253 are payed out. As a result, relative to the view of FIG. 3B, pulley221 rotates counterclockwise, pulley 222 rotates clockwise, and cables251, 252, 253, and 254 do not slide or slip on pulley 221 or 222 whenclosing jaws 242 and 244. Opening blades 242 and 244 switches thetension in cables 251, 252, 253, and 254 and reverses the directions ofrotation of pulleys 221 and 222 but still avoids sliding on pulleys 221and 222.

Some of cables 251, 252, 253, and 254 can slide or slip in the groove ofor move relative to the rotation of pulleys 221 or 222 when the yawangle of blades 242 and 244 is being changed. For example, the yaw ofend effector 200 can be changed by pulling in (or paying out) equallengths of cables 251 and 253 while paying out (or pulling in) the samelengths of cables 252 and 254. When the pitch angle of end effector 200is zero as shown in FIGS. 3A and 3B, at least one of cables 251 and 253will slide on pulley 221, and at least one of cables 252 and 254 willslide on pully 222. The sliding friction that resists a cable's movementwill then depend on the wrap angle of the cable on its associated pulley221 or 222 and the component cable tension pulling the cable on to itspulley 221 or 222. With a pitch angle of zero, the wrap angles of cableson pulleys 221 and 222 are relatively small and the sliding friction isrelatively small.

A non-zero pitch angle of end effector 200 will cause cable 251 to havea wrap angle around pulley 221 that differs from the wrap angle of cable253 around pulley 221 and cause cable 252 to have a wrap angle aroundpulley 222 that differs from the wrap angle of cable 254 around pulley222. FIG. 3C illustrates how a large pitch angle of distal clevis 230causes cable 251 to have a large wrap angle on pulley 221 and liftscable 253 off of pulley 221. When high tension is applied to cables 251and 253 to causes blades 242 and 244 to rotate in the same direction,cable 253 slides on solid surfaces of devises 220 and 230, but pulley221 rotates as cable 251 moves, resulting in lower friction for cable251 than if cable 251 were sliding over an integral sliding surface indistal clevis 230.

Both cables 251 and 253 may contact pulley 221 but have different wrapangles when distal clevis 230 has other pitch angles. In theseconfigurations, the cable 251 or 253 exerting greater force on pulley221 will rotate with pulley 221 during rotation of blades 242 and 244 tochange the yaw angle of end effector 200. The other cable 253 or 251then slides on pulley 221, but that cable has smaller force/wrap angleon pulley 221. Similarly, cables 252 and 254 will generally havedifferent wrap angles on pulley 222, and the cable that exerts thegreater force on pulley 222 (and that would therefore experience greatersliding friction) moves with the rotation of pulley 222.

The use of a single pulley for a pair of cables as in end effector 200thus usually reduces cable friction when compared to cables ridingsolely on solid fixed surfaces. Use of one pulley for two cables alsoconserves space and reduces part count when compared to a traditionalpulley system including a pulley for each cable (or four pulleys totalfor a four cable system). However, alternative embodiments of theinvention can employ other pulleys structures to reduce cable friction.Alternatively, to provide lower component count and costs, pulleys 221and 222 can be eliminated and guide channels such as described in theco-filed patent application entitled, “Four-Cable Wrist with SolidSurface Cable Channels,” which was incorporated by reference above,could be used to guide the drive cables and define the moment arm fortorques causing pitch rotations.

For example, FIGS. 4A, 4B, and 4C show three views of a wrist mechanism700 in accordance with an embodiment of the invention. As illustrated inFIG. 4A, wrist mechanism 700 includes a proximal clevis 720, a distalclevis 730, and an effector 740. Effector 740 includes jaws 742 and 744,each having a grip portion attached to a circular hub. Cables 751, 752,753, and 754 are attached to effector 740, extend along solid surfacesof guide channels in effector 740, distal clevis 730, and proximalclevis 720, and from there extend back through main tube 110 to abackend mechanism (e.g., backend mechanism 120 of FIG. 1). The low partcount of wrist mechanism 700 and the small number of drive cables 751,752, 753, and 754 employed facilitate implementation of a small diameterfor wrist mechanism 700 and main tube 110. Additionally, the low partcount allows cost effective use of wrist mechanism in a single-useinstrument, i.e., an instrument that is disposed of after a singlemedical procedure, instead of being an instrument that must besterilized for subsequent use.

The partial cutaway view of wrist mechanism 700 in FIG. 4B shows howproximal clevis 720 can extend into and attach to main tube 110. A pin725 in proximal clevis 720 attaches distal clevis 730 to proximal clevis720 but allows distal clevis 730 to rotate about a pivot axis (sometimesreferred to herein as the pitch axis) defined by pin 725. Proximalclevis 720 includes guide channels 722 for cables 751, 752, 753, and754, and openings 724 of the guide channels 722 provide a range ofmotion for cables 751, 752, 753, and 754 that directs cables 751, 752,753, and 754 into guide channels 732 of proximal clevis 730. In anexemplary embodiment, openings 724 of guide channels 722 are narrow inthe direction parallel to pin 725 in order to direct cables 751, 752,753, and 754 into respective guide channels 732 in distal clevis 730 butfan out in a direction perpendicular to pin 725 to keep cable frictionlow over the range of pitch angles that wrist mechanism 700 provides fordistal clevis 730. Similarly, openings 734 of guide channels 732 nearestproximal clevis 720 are narrow in a direction parallel to the pitch axisand pin 725 but fan out in a direction perpendicular to pin 725 toaccommodate pitch rotations and avoid pinching cables 751, 752, 753, and754.

Guide channels 732 in distal clevis 730 define a radius about pin 725 atwhich cables 751, 752, 753, and 754 act on distal clevis 730 whenrotating distal clevis 730 about pin 725, i.e., about the pitch axis. Inorder for the moment arm of the torque applied by the cables to beconstant throughout the range of pitch motion of wrist mechanism 700,guide channels 732 have surfaces approximately in the shape of circulararcs. When distal clevis 730 is in the position illustrated in FIG. 4C,cable 753 has a portion that rests against a lower guide surfacesubtending a circular arc about the pitch axis of pin 725, and thedistance between the pitch axis and the contact point of cable 753 onthe lower surface of guide channel 732 is the moment arm for torqueapplied through cable 753. In the view of FIG. 4C, distal clevis 730rotates clockwise when the backend mechanism pulls in cable 753. Ifclockwise rotation continues from the illustrated position, cable 753will remain on the surface and act at a constant moment arm until distalclevis 730 reaches the limit of its range of motion. Further, throughthe entire motions, the surfaces of guide channels 732 that are circulararcs pull in and play out equal lengths of cable as distal clevis 730rotate, thereby avoiding cable slack.

The cross-section of distal clevis 730 in FIG. 4C further illustrateshow guide channels 732 extend through distal clevis 730 and directcables 751, 752, 753, and 754 into circular guide channels 746 that areintegrated into jaws 742 and 744 of effector 740. In particular, fourguide channels 732 tunnel through distal clevis 730 for the four cables751, 752, 753, and 754. Openings 736 of guide channels 732 nearesteffector 740 direct cables 751, 752, 753, and 754 into respective guidechannels 746 in jaws 742 and 744.

A pin 735 in distal clevis 730 is perpendicular to pin 725 and defines apivot axis, sometimes referred to as the yaw axis or grip axis, foreffector 740 as a whole or jaws 742 and 744 individually. (The yaw axisand the grip axis coincide in wrist mechanism 700.) Guide channels 746of jaws 742 and 744 are circular and centered on pin 735, so that theradius of channels 746 is the moment arm for torques that cables 751,752, 753, and 754 apply to jaws 742 and 744 when rotating jaws 742 and744 or when maintaining a gripping force of jaws 742 and 744. The termgripping is used herein in a general sense since the action of jaws 742and 744 depend on the work tips of jaws 742 and 744. In the illustratedembodiment of FIGS. 4A, 4B, and 4C, the working tips of jaws 742 and 744have a surface for gripping and may be used, for example, in forceps orcautery applications. Alternatively, “gripping,” which closes jaws 742and 742, may be a cutting action when the tips of jaws 743 and 744 areblades that cooperatively cut as a scissors. Gripping can thus performdifferent functions depending on the nature of effector 740.

The paths of cables 751, 752, 753, and 754 through wrist mechanism 700do not employ pulleys. Instead of pulleys, wrist mechanism 700 guidescables 751, 752, 753, and 754 as described above using solid surfaces(i.e., the surfaces of guide channels 722 and 732) that are integral todevises 720 and 730. At some points, the guiding surfaces cradleopposing sides of the cable. For example, top and bottom surfaces ofcable 753 as shown in FIG. 4C contact guide surface 732 at an inflectionpoint 737 where the curvature of cable 753 changes. The solid guidesurfaces are also curved to eliminate the need for large cable wrapangles and to maintain a fixed cable radius or moment arm. Large wrapangles were necessary in some prior wrist mechanisms to maintain aconstant cable radius about the pivot axis throughout the range ofmotion. The surfaces of guide channels 722 and 732 can additionally beshaped to retain (or avoid derailment of) cables 751, 752, 753, and 754and to keep cables 751, 752, 753, and 754 within the diameter constraintof a cannula through which wrist mechanism 700 passes during a minimallyinvasive medical procedure.

Guiding cables 751, 752, 753, and 754 experience less friction whencompared to wrist mechanisms with larger cable wrap angles. Friction ofcables 751, 752, 753, and 754 against distal clevis 730 and elsewheremay also be reduced through selection of the materials used. Inparticular, distal clevis 730 can be made of a plastic that provides lowfriction against the material of cables 751, 752, 753, and 754.Additionally, in some embodiments, cables 751, 752, 753, and 754 includeportions of stranded metal cable that may be swaged to provide smoothercable surfaces that lower friction. The reduced cable friction allowspulleys to be deleted while maintaining clinically acceptable forces,torques, and precision and fidelity of motion for wrist mechanism 700.Avoiding the use of pulleys reduces the space requirements of wristmechanism 700, allowing wrist mechanism 700 to have a clinicallybeneficial smaller working volume. Eliminating pulleys also reduces thecost.

Cables 751 and 752 attach to jaw 742 of effector 740, and cables 753 and754 attach to jaw 744 of effector 740. The attachment of cables 751 and752 to jaw 742 is such that pulling in a length of one cable 751 or 752while releasing the same length of the other cable 752 or 751 causes jaw742 to rotate about pin 735. Similarly, the attachment of cables 753 and754 to jaw 744 is such that pulling in a length of one cable 753 or 754while releasing the same length of the other cable 754 or 753 causes jaw744 to rotate about pin 735. Many techniques for attaching cables 751,752, 753, and 754 could be employed. For example, in a typicalattachment, cables 751 and 752 (or cables 753 and 754) are opposite endportions of a cable loop that extends around circular arc about pin 735that guide channel 746 defines in jaw 742 (or 744), and an attachmentcan be created by a knot tied in or a crimp fastened on the loop and fitinto a matching notch (not shown) in guide channel 746. However,reliably attaching a crimp to some cable materials, e.g., non-conductivecable materials can present challenges. To avoid crimping, the cableloop may terminate through a high-friction pathway in jaw 742 or 744, sothat friction prevents cables 751, 752, 753, and 754 from slippingrelative to jaws 742 or 744.

FIG. 5A shows a jaw 742A attached to a cable loop 750 having portionsthat extend back into main tube 110 as to cables 751 and 752. Loop 750extends along circular arcs of guide channel 746 of jaw 742A into a highfriction path 748A, and back out along another circular arc of guidechannel 746. Path 748A is substantially co-planar with guide channel 746and includes multiple sharp bends. Contact between cable loop 750 andthe surface of jaw 742A at the bends in path 748A creates friction thatprevents or resists sliding of cable 750, each bend increasing thefrictional force that acts to retain cable loop 750 against pullout.Cable loop 750 has no crimp attached.

FIG. 5B shows a jaw 742B using an alternative high friction path 748B inwhich cable loop 750 is threaded through several holes in jaw 742B.Contact of cable loop 750 with jaw 742B at the bends in cable loop 748B(including at locations where cable loop 750 passes through jaw 742B)creates friction that resists or prevents sliding of cable loop 750.Accordingly, a crimp is not required to attach cable loop 750 to jaw742B. Assembly of a wrist mechanism using high friction path 748Brequires threading of cable through holes in jaw 742B, but oncethreaded, cable loop 750 is solidly retained in jaw 742B, which may makeassembly of a wrist using high friction path 748B of FIG. 5B simplerthan assembly of a wrist using high friction path 748A of FIG. 5A.

The jaw attachments without crimps eliminate the space requirement ofcrimps and the cost associated with crimping. The attachments withoutcrimps are also advantageous for some cable materials (e.g. non-metalliccables) for which crimping can be troublesome. As described furtherbelow, non-metallic cables can be useful as electrical insulators incauterizing instruments. Even instruments that do not require electricalinsulation, non-metallic cables may provide reduced friction, wear, andparticulate generation against mating surfaces in the wrist mechanism.

Changing the pitch, yaw, or grip of the wrist mechanism 700 describedabove generally requires movements or actions respectively applied tofour cables 751, 752, 753, and 754. FIG. 6A shows a simplified view ofwrist mechanism 700 and illustrates processes for changing the pitch,yaw, and grip of jaws 742 and 744. The illustrated processes cangenerally be performed one at a time or simultaneously in any desiredcombination to change the pitch, yaw, and grip of mechanism 700. FIG. 6Bshows wrist mechanism 700 in more detail to illustrate rotation axes ofwrist mechanism 700 and is described here simultaneously with FIG. 6A.

Pitch axis rotations, i.e., rotations 425 in FIG. 6B, rotate distalclevis 730 about the pitch axis defined by pin 725. For clockwiserotation about the pitch axis, a backend mechanism (not shown) pulls inidentical lengths of cables 753 and 754 while releasing the same lengthsof cables 751 and 752. Cables 753 and 754 apply forces to distal clevis730 at moment arms defined by the guide channels of cables 753 and 754through distal clevis 730. Similarly, for counterclockwise rotation ofclevis 730 about the pitch axis, the backend mechanism pulls inidentical lengths of cables 751 and 752 while releasing the same lengthsof cables 753 and 754.

Yaw rotations, i.e., rotations 435 in FIG. 6B, corresponds to bothrotating jaws 742 and 744 in the same direction and through the sameangle. In particular, the backend mechanism pulling in a length of cable752 and releasing an equal length of cable 751 will cause jaw 742 torotate in a clockwise direction about the axis of pin 735. For thisrotation, the guide channel in jaw 742 defines the moment arm at whichcable 752 applies a force jaw 742, and the resulting torque causes jaw742 to rotate clockwise and cables 751 and 752 to slide on the solidsurface of guide channels in distal clevis 730. If at the same time thebackend mechanism pulls in a length of cable 754 and releases the samelength of cable 753, jaw 744 will rotate clockwise through an angle thatis the same as the angle through which jaw 742 rotates. Accordingly,jaws 742 and 744 maintain their positions relative to each other androtate as a unit through a yaw angle. Counterclockwise rotation of theeffector including jaws 742 and 744 is similarly accomplished when thebackend mechanism pulls in equal lengths of cables 751 and 753 whilereleasing the same lengths of cables 752 and 754.

Grip rotations, i.e., rotations 445 in FIG. 6B, are achieved by rotatingjaws 742 and 744 in opposite directions by the same amount. To open thegrip of jaws 742 and 744, the backend mechanism pulls in equal lengthsof cables 751 and 754 while releasing the same lengths of cables 752 and753, causing jaws 742 and 744 to rotate in opposite directions away fromeach other. To close the grip of jaws 742 and 744, the backend mechanismpulls in equal lengths of cables 752 and 753 while releasing the samelengths of cables 751 and 754, causing jaws 742 and 744 to rotate inopposite directions toward each other. When faces of jaws 742 and 744come into contact, the tension in cables 752 and 753 can be kept greaterthan the tension in cables 751 and 754 in order to maintain grippingforces.

FIG. 6A illustrates that portions 452 and 453 of cables 752 and 753,respectively, can be made stiffer or thicker than corresponding portionsof cables 751 and 754 to accommodate the higher or maintained tensionsused for gripping. This can be achieved by fusing the ends of cableloops corresponding to cable 752 or 753 with heavier material. In atypical embodiment of the invention, portions of cables 751, 752, 753,and 754 having larger flexing during cable movement can be made of aflexible material such as a stranded metal cable. Relatively straightportions of each cable (e.g., portions extending back through the maintube) in some embodiments can be less flexible material such ashypotubes or similar structures that have advantages in cost andimmunity to stretching, and in such an embodiment, larger hypotubes canbe used for portions 452 and 453 of cables 752 and 753. The effectivestiffness of each of the four drive cables 751, 752, 753, and 754 canthus be controlled advantageously for improved clinical performance. Inparticular, the effective stiffness of drive cables 752 and 753 thatcause jaws 742 and 744 to close is greater than the stiffness of drivecables 751 and 752 that cause jaws 742 and 744 to open. This arrangementminimizes cable slack, improving the fidelity of motion of wristmechanism 700. Materials, diameters, and lengths (e.g., of portions 452and 453) are controlled to affect desired stiffness. Not using thelarger structures in cables 751 and 754 saves cost and space.

A backend mechanism can change the pitch, yaw, or grip of scissors 240or any combination of pitch, yaw, and grip through manipulation ofcables 251, 252, 253, and 254 as described above. For example, thebackend mechanism pulling in the same length of cables 251 and 252 whilereleasing an equal length of cables 253 and 254 causes clevis 230 torotate about pin 225, e.g., to pitch downward in FIG. 3B. Similarly, thebackend mechanism pulling in the same length of cables 253 and 254 whilereleasing an equal length of cables 251 and 252 causes clevis 230 topitch upward in FIG. 3B. Pulling in a length of one cable 251 or 252while releasing an equal length of the other cable 252 or 251 causesblade 242 to rotate about pin 235. Similarly, pulling in a length of onecable 253 or 254 while releasing an equal length of the other cable 254or 253 causes blade 244 to rotate about pin 235. The backend mechanismcan thus change the yaw of scissors 240 by rotating both blades 242 and244 in the same direction through the same angle. The grip of scissors240 can be changed by rotating both blades 242 and 244 in oppositedirections through the same angle.

Scissors 240 are designed such that the constraining surfaces thatmaintain blade cutting forces are all metal. In particular, pin 235 hasan expanded head portion and an opposite end cap that constrain blades242 and 244 from separating during cutting. This ensures consistentclosing force of blades 242 and 244 throughout their life while makingfor a low friction interface when pivoting in distal clevis 230.Further, distal clevis 230 can be made of plastic or other insulatingmaterial and does not require the strength/rigidity to prevent blades242 and 244 from being pushed apart during cutting.

The use of metal cables 251, 252, 253, and 254 attached to metal blades242 and 244 for actuation also permits use of cables 251, 252, 253, and254 to electrically energize blades 242 and 244. This avoids the needfor additional conductors in main tube 110 and for additional electricalconnectors in end effector 200. In an embodiment used for monopolarscissors, all metal parts in end effector 200 are electrically energizedwith the same signal at the same time, e.g., whenever a cauterizingfunction of scissors 240 is activated. As mentioned above, main tube 110can be made of insulating material and a cover 260, which is held onmain tube 100 using compression ring 262, can encapsulate cables 251,252, 253, and 254 and most of the components of end effector 200,leaving blades 242 and 244 as the only electrically energized componentsthat are exposed and able to contact the patient. Additionally,insulating plastic components can be used throughout the instrumentwhere strength requirements permit, for example, proximal clevis 220 anddistal clevis 230 can be made of plastic or other insulating material.Plastic components may also reduce friction where cables ride on solidsurfaces.

Seals may be employed at the end of main tube 200 to isolateelectrically energized cables from conductive fluids that may be incontact with the instrument during a medical procedure. The partialcutaway view of end effector 200 in FIG. 3A shows how proximal clevis220 can extend into main tube 110 and how multiple seals 270 and 275 canbe used to prevent fluid flow. Limiting contact to conductive fluids isdesired because liquid in contact with energized cables can directlyconduct the full working voltage from the cables to the patient andcause alternate site burns. The seals create a barrier to break that thedirect conductive path. Additionally, the signal conducted through maintube 110 has a capacitive coupling to the surrounding environmentoutside main tube 110. This capacitive coupling can cause currents insurrounding liquids, and those currents waste power, lower the workingvoltage on blades 242 and 244, and could cause alternate site burns. Thestrength of the capacitive coupling and the magnitude of the capacitiveleakage currents depend on factors such as the diameter and length ofconductor (e.g., cable 251, 252, 253, or 254), the insulating propertiesof main tube 110, and the separation between the conductor within maintube 110 and the external environment. If main tube 110 were to fillwith conductive fluid, the effective distance between the conductorportion inside main tube 110 and the external environment would besmaller and capacitive coupled current leaked to the patient would begreater.

An embodiment of end seal 270 is illustrated in FIG. 7. Seal 270 asshown has a diameter that fits tightly inside main tube 110 and fourprojections 410 through which cables 251, 252, 253, and 254 extend. Seal270 can be made of silicon or a similar flexible material capable ofsealing against main tube 110 and cables 251, 252, 253, and 254 andflexing when cables 251, 252, 253, and 254 move for actuation ofscissors 240.

A variety of multi-seal systems could be employed to isolate a patientor user of the instrument from electrical burn hazards. FIG. 3A showsone example where end effector 200 employs cover 260 and seals 270 and275 in main tube 110 for these purposes. More generally, seals can beused around the cables and between the proximal clevis and the main tubeto limit fluid flow into main tube, which could flow out the back end ofthe instrument. A rib seal can be used between the proximal clevis andthe tip cover to obstruct fluid flow from the inside to the outside ofthe tip cover, which is important because fluid from the inside of thetip cover would be at full cautery voltage and could cause alternatesite burns in a patient. Redundant seals can also be used to improvereliability.

Electrical connection to at least one of cables 251, 252, 253, or 254can be made in the backend mechanism that manipulates cables 251, 252,253, or 254. FIG. 8A shows an exploded view of a portion of a backendmechanism 500 in accordance with an embodiment of the inventionpredominantly employing gears and levers to control movement of a wristmechanism or end effector. The illustrated portion of backend mechanism500 couples to four drive cables 571, 572, 573, and 574 and includes achassis 510, three drive shafts 512, 513, and 514, three toothedcomponents 520, 530, and 540, and two levers 550 and 560. The components510, 520, 530, 540, and 550 and 560 can be made of any suitably durablematerial such as molded or machined plastic or metal depending on therequired loads and tolerances of the individual components. However,components such as chassis 510 and drive gears 512, 513, and 514 whichare externally accessible are preferably made of plastic or anotherinsulating material. As described further below, cables 571, 572, 573,and 574 can correspond to cables 251, 252, 253, and 254 and connect toan end effector of the type described above with reference to FIGS. 2A,2B, 3A, and 3B. However, backend mechanism 500 can more generally beused in any instrument that can be electrically energized by drivecables and uses connections of four drive cables to three motor drivenaxes.

Chassis 510 may have a footprint chosen for connection to a roboticcontrol system containing motors that operate drive shafts 512, 513, and514. In particular, chassis 510 may be shaped such that drive shafts512, 513, and 514 when fit into chassis 510 are positioned to be engagedand rotated by a robotic control such as the da Vinci system availablefrom Intuitive Surgical, Inc.

Drive shaft 512 acts as a pinion that engages a rack portion of toothedcomponent 520. Toothed component 520 is attached to cable 572 and movesin a straight line to pull in or release a length of cable 572 as gear512 turns. Toothed component 520 also includes an arm containing anadjustment screw 522 that contacts lever 550. In particular, adjustmentscrew 522 contacts lever 550 at an end opposite to where cable 571attaches to lever 550. A pivot point or fulcrum for lever 550 is ontoothed component 540, which acts as a rocker arm as described furtherbelow. In operation, as toothed component 520 moves, adjustment screw522 causes or permits rotation of lever 550 about the pivot point sothat lever 550 can pull in or release cable 571. The connection of cable571 to lever 550 and the contact point of adjustment screw 522 on lever550 can be made equidistant from the pivot point of lever 550, so thatwhen toothed component 520 pulls in (or releases) a length of cable 572,lever 550 releases (or pulls in) the same length of cable 571.Adjustment screw 522 permits adjustment of the tension in cable assembly571 and 572 by controlling the orientation of lever 550 relative to theposition of toothed component 520.

Drive shaft 513 similarly acts as a pinion that engages a rack portionof toothed component 530. Toothed component 530 is attached to drivecable 573 and moves in a straight line to pull in or release a length ofcable 573 as gear 513 turns. Toothed component 520 also includes an armcontaining an adjustment screw 532 that contacts lever 560 at an endopposite to where cable 574 attaches to lever 560. A pivot point orfulcrum for lever 560 is on rocker arm 540 as described further below,and the distance of the connection of cable 574 from the pivot point oflever 560 can be made the same as the distance from the pivot point oflever 560 to the contact point of adjustment screw 532 on lever 560. Asa result, when toothed component 550 pulls in (or releases) a length ofcable 573, lever 560 releases (or pulls in) the same length of cable574. Adjustment screw 532 permits adjustment of the tension in cableassembly 573 and 574 by controlling the orientation of lever 560relative to the position of toothed component 530.

Drive shafts 512 and 513 can be operated to change the yaw angle or thegrip of a wrist mechanism using the processes described above. Forexample, when cables 571, 572, 573, and 574 respectively correspond tocables 251, 252, 253, and 254 of FIG. 3B, turning gears 512 and 513 atthe same speed in the same direction or in opposite directions willchange the grip or yaw of scissors 240.

Drive shaft 514 engages an internal sector gear portion of rocker arm540. Rocker arm 540 has a pivot 542 attached to chassis 510, so that asdrive shaft 514 turns, rocker arm 540 rotates about pivot 542. Rockerarm 540 also includes protrusions (not visible in FIG. 8A) that act aspivot points for levers 550 and 560. These protrusions can be locatedequidistant from pivot 542, so that as rocker arm 540 rotates, one pivotmoves closer to the end effector and the other pivot moves further fromthe end effector by an equal amount. If toothed components 520 and 530are moved at the appropriate speeds and directions to maintain theorientations of levers 550 and 560, rotation of rocker arm 540 will pullin (or release) equal lengths of cables 571 and 572 and release (or pullin) the same lengths of cables 573 and 574. Backend mechanism 500 canthus be used to perform a pitch change as described above with referenceto FIG. 3B when cables 571, 572, 573, and 574 respectively correspond tocables 251, 252, 253, and 254, but the pitch change requires coordinatedrotations of all three drive shafts 512, 513, and 514. Such coordinatedrotations can be implemented in software of a robotic control system.

A connector 590 and a wire 592 can be used to connect an external powersupply or generator (not shown) to one or more of cables 571, 572, 573,and 574. The power supply can be of the same type currently known inmonopolar cauterizing instruments, and connector 590 can be of anydesired type required for connection to the particular power supply.Alternatively, connector 590 can be a standard connector type such as abanana jack that connects to the power supply through an adapter cable(not shown).

FIG. 8B shows a cross-sectional view of backend mechanism 500 whenassembled with additional components not shown in FIG. 8A. Asillustrated, backend mechanism 500 includes drive shafts 512, 513, and514 that respectively engage toothed components 520, 530, and 540, and arobotic control system coupled to backend 500 can rotate drive shafts512, 513, and 514 to control the pitch, yaw, and grip of a wristmechanism or end effector (not shown). Cables 571, 572, 573, and 574extend from the end effector at a distal end of a main tube 110, throughmain tube 110 and into backend mechanism 500. In the illustratedembodiment, wire 592 makes electrical connection to cable 573 at toothedcomponent 530. Accordingly, wire 592 must provide sufficient slack toaccommodate the range of motion of toothed component 530. Alternatively,wire 592 may be connected to any one or more of cables 571, 572, 573,and 574.

Main tube 110 is attached in backend mechanism 500 to a helical gear580, which is coupled to a drive shaft 511 through an interveninghelical gear 582. When a control system rotates drive gear 511, helicalgears 582 and 580 rotate main tube 110 and thereby change the roll angleof the end effector at the distal end of main tube 110.

FIG. 8B also shows a circuit board 594, which may be included in backendmechanism 500. Circuit board 594 can provide an interface for connectionto a robotic control system. Circuit board 594 would typically storeinformation about the instrument such as an identifier identifying thetype of instrument and operating parameters of the instrument such as acount of the number of uses of the instrument. In the case of a singleuse instrument, the control system would check and change the count ofthe number of uses when the instrument is used. The control system candisable uses of a single-use instrument when the use count indicates theinstrument has already been used.

Backend mechanism 500 as illustrated in FIG. 8B also includes a cover516 to enclose mechanical and electrical systems in backend mechanism500. Cover 516 can thus isolate electrically charged cables fromunintended contact. A latch system 518 can be used to lock backendmechanism in a docking port of a control system.

Pulleys and capstans can be used in a backend mechanism in place of sometoothed components of FIGS. 8A and 8B. FIG. 9A shows a backend mechanism600 in accordance with an embodiment of the invention employing cables,pulleys, and capstans. Backend mechanism 600 includes a chassis 610,four drive shafts 611, 612, 613, and 614, a pair of capstans 620 and630, a rocker arm 640 on which pulleys 642 and 643 are mounted, helicalgears 580 and 582, and electrical components 590, 592, and 594. Fourdrive cables 671, 672, 673, and 674, which are connected to an endeffector (not shown), extend through main tube 110 into backendmechanism 600. Cables 671, 672, 673, and 674 can respectively correspondto cables 251, 252, 253, and 254, which are connected to end effector200 of FIGS. 3A and 3B. However, backend mechanism 600 can moregenerally be used in any instrument for which an electrically energizeddrive cable and connection of four cables to three motor driven axes isdesired.

The shape of chassis 610 is generally selected to have a footprintcorresponding to a mounting or docking port on a robotic control system.Backend mechanism 600 may thus be fitted to a control system so thatdrive shafts 611, 612, 613, and 614 are mechanically coupled to motorsin the control system. The control system is then able to rotate driveshafts 611, 612, 613, and 614 through precise angles that may beselected by software to achieve the desired operation or movement of theinstrument.

Cables 671 and 672 pass from main tube 110, around one or more pulleys642, and wrap around capstan 620. The wrapping of cables 671 and 672around capstan 620 is such that when capstan 620 turns, a length of onecable 671 or 672 is pulled in and an equal length of the other cable 672or 671 is fed out. Similarly, cables 673 and 674 pass from main tube110, around one or more pulleys 643, and are wrapped around capstan 630,so that when capstan 630 turns, a length of one cable 673 or 674 ispulled in and an equal length of the other cable 674 or 673 fed out.Drive shafts 612 and 613 are respectively coupled to turn capstan 620and 630. A control system can thus turn drive shafts 612 and 613 tochange the yaw angle or the grip of an end effector using the processesdescribed above. For example, when cables 671, 672, 673, and 674respectively correspond to cables 251, 252, 253, and 254 of FIG. 3B,turning drive shafts 612 and 613 at the same speed in the same directionor in opposite directions will open, close, or change the yaw ofscissors 240.

Pulleys 642 and 643 could have deep grooves, and a keeper 690 as shownin FIG. 9B could be attached to the pivot pins of pulleys 642 and 643 tohelp prevent electrified cables from jumping off of pulleys 642 or 643.Keeper 690 can also keep pulleys 642 and 643 from coming off theirrespective pins when a cable goes slack or the instrument is upsidedown. Pulleys 642 and 643 are mounted on rocker arm 640. Rocker arm 640has a sector gear portion that engages drive shaft 614 and is coupled tochassis 610 to rotate about a pivot axis when drive shaft 614 turns. Thesector gear portion and pivot of rocker arm 640 are designed so thatrotation of rocker arm 640 primarily causes one pulley 642 or 643 tomove toward its associated capstan 620 or 630 and the other pulley 643or 642 to move away from its associated capstan 630 or 620. Thiseffectively pulls in lengths of one pair of cables 671 and 672 or 673and 674 and releases an equal length of the other pair of cables 673 and674 or 671 and 672. Backend mechanism 600 simply through rotation ofdrive shaft 614 can thus change the pitch in an end effector asdescribed above with reference to FIG. 3B when cables 671, 672, 673, and674 respectively correspond to cables 251, 252, 253, and 254.

Backend mechanism 600 can control the roll angle of a wrist mechanism atthe distal end of main tube 110 using drive shaft 611 to turn helicalgears 582 and 580, which are coupled to main tube 110 in the same manneras described above.

Cables 671, 672, 673, and 674 in backend mechanism 600 wind or wraparound pulleys 642 and 643 and capstans 620 and 630 and must be able toflex when capstans 620 and 630 rotate. Accordingly, portions of cables671, 672, 673, and 674 in backend mechanism 600 require flexibility andmay be, for example, stranded metal cable that can be flexed repeatedlyaround relatively sharp turns without damage. Accordingly, each cable671, 672, 673, and 674 may include three portions, a stranded cableportion at the end effector, a more rigid portion (e.g., a hypotube)extending through the straight portion of main tube 110, and a secondstranded cable portion in backend mechanism 600. For comparison, backendmechanism 500 of FIG. 8B moves cables 571, 572, 573, and 574 in nearlylinear motions and does not require significant flexing of cables 571,572, 573, and 574 around pulleys or other sharp bends. Accordingly, theportions of cables 571, 572, 573, and 574 in backend mechanism 500 canbe relatively rigid structures such as hypotubes.

Wire 592 and electrical connector 590, which can be used for connectionof a power supply or generator as described above, is connected to thehub or pivot pin of pulleys 642 in the illustrated embodiment of FIG.9A. Alternatively, electrical connections to the pivot pins of pulleys642 and 643 can be made through keeper 690 which contacts the pivotpins. Pulleys 642 and 643 and the pivot pins can be made of anelectrically conductive material such as metal, so that one or more themetal cables 671, 672, 673, and 674 are electrically energized when wire592 is electrically energized. Since pulleys 642 and 643 and keeper 690move when rocker arm 640 rotates, wire 592 requires sufficient slack toaccommodate the range of motion. Backend mechanism 600 of FIG. 9A or 9Blike backend mechanism 500 of FIG. 8B also includes a circuit board 594with circuits and connectors for electrical systems that may be employedin a medical instrument that connects to a robotic control system.

Embodiments of the invention as described above can reduce the number ofcomponents in an electrified medical instrument and thereby reduce coststhrough use of drive cables as electrical conductors. Reduction of thecost has obvious benefits, but also enables the creation of single-useinstruments that are cost competitive (per case) when compared toexisting reusable instruments. A single-use instrument has furtherbenefits of eliminating reprocessing and sterilization at the hospitaland allows further cost savings during manufacture of the instrumentsbecause components do not need to be designed and verified to enablereprocessing. Additionally, disposable scissors will ensure the cuttingblades are new and sharp.

Although the invention has been described with reference to particularembodiments, the description is only an example of the invention'sapplication and should not be taken as a limitation. In particular,although the above description concentrated on embodiments of theinvention that are monopolar scissors, aspects of the invention can beemployed in other electrically energized medical instruments such asinstruments having non-gripping end effectors such as wire loops orscalpels or having general electrodes with hook shapes, spatula shapes,ball-end shapes, needle shapes, or other shapes. A gripping end effectorsuch as forceps could also be energized to provide an instrument that isusable to grasp tissue and/or apply monopolar cautery energy. Variousother adaptations and combinations of features of the embodimentsdisclosed are within the scope of the invention as defined by thefollowing claims.

What is claimed is:
 1. An apparatus, comprising: a shaft comprising adistal end portion and a proximal end portion; a wrist mechanism coupledto the distal end portion of the shaft, actuation of the wrist mechanismproducing movement of a distal portion of the wrist mechanism relativeto a proximal portion of the wrist mechanism, the wrist mechanism havinga wrist cable path; an end effector coupled to the distal portion of thewrist mechanism, actuation of the end effector producing movement of theend effector relative to the distal portion of the wrist mechanism; acable pair routed through the wrist cable path, a first end of the cablepair being coupled to the end effector; and a transmission coupled to aportion of the shaft, the transmission comprising an input connection,an input shaft, a transmission cable path, and an adjustment mechanism,the input connection being configured to be driven by an actuator of acontrol mechanism, the input shaft operatively coupled to the inputconnection and being configured to move a portion of the cable pair toactuate the end effector via rotation of the input connection, the cablepair being routed through the transmission cable path within thetransmission between the input shaft and the shaft, the adjustmentmechanism being between the input connection and the proximal endportion of the shaft and having a guide portion in contact with thecable pair, the guide portion being configured to move to change alength of the transmission cable path.
 2. The apparatus of claim 1,wherein the adjustment mechanism comprises a first arm portion with theguide portion mounted thereon, the guide portion comprising a pulleycoupled to the first arm portion, the pulley defining a portion of thetransmission cable path.
 3. The apparatus of claim 2, wherein rotationof the first arm portion causes the pulley to move relative to the inputconnection.
 4. The apparatus of claim 2, wherein the guide portion is afirst guide portion, the transmission cable path is a first transmissioncable path and the adjustment mechanism further comprises a second armportion with a second guide portion mounted on the second arm portionand a second cable pair in contact with the second guide portion, thesecond cable pair being routed along a second transmission cable path.5. The apparatus of claim 4, wherein the adjustment mechanism lengthensthe first transmission cable path while shortening the secondtransmission cable path.
 6. The apparatus of claim 5, wherein the firstarm portion and the second arm portion are operatively connected suchthat the first arm portion and the second arm portion rotate together.7. The apparatus of claim 4, wherein the first arm portion and thesecond arm portion are between the input connection and the proximal endportion of the shaft.
 8. The apparatus of claim 7, wherein the first armportion and the second arm portion are a part of a rocker arm.
 9. Anapparatus, comprising: a shaft comprising a distal end portion and aproximal end portion; a wrist mechanism coupled to the distal endportion of the shaft, actuation of the wrist mechanism producingmovement of a distal portion of the wrist mechanism relative to aproximal portion of the wrist mechanism, the wrist mechanism having awrist cable path; an end effector coupled to the distal portion of thewrist mechanism, actuation of the end effector producing movement of theend effector relative to the distal portion of the wrist mechanism; acable pair routed through the wrist cable path, a first end of the cablepair being coupled to the end effector; and a transmission coupled to aportion of the shaft, the transmission comprising an input connection,an input shaft, a transmission cable path, and an adjustment mechanism,the input connection being configured to be driven by an actuator of acontrol mechanism, the input shaft operatively coupled to a second endof the cable pair and configured to move the second end of the cablepair, the cable pair being routed through the transmission cable pathwithin the transmission between the input shaft and the shaft, theadjustment mechanism having a guide portion in contact with a portion ofthe cable pair, the guide portion having a link that rotates between afirst position and a second position to change a length of thetransmission cable path, wherein a portion of the link is closer to theinput connection in the first position than in the second position. 10.The apparatus of claim 9, wherein the guide portion includes a pulleycoupled to the link, the pulley defining a portion of the transmissioncable path.
 11. The apparatus of claim 10, wherein rotation of the linkcauses the pulley to move relative to the input connection.
 12. Theapparatus of claim 10, wherein the pulley is a first pulley, the guideportion is a first guide portion, and the adjustment mechanism furthercomprises a second guide portion that is mounted on a second arm portionand includes a second pulley.
 13. The apparatus of claim 12, wherein thefirst pully is on a first arm portion with the first arm portion and thesecond arm portion being operatively connected such that the first armportion and the second arm portion rotate together.
 14. The apparatus ofclaim 9, wherein the transmission cable path is a first transmissioncable path, the cable pair is a first cable pair, and the transmissionfurther comprises a second transmission cable path with a second cablepair routed therethrough, wherein the adjustment mechanism lengthens thefirst transmission cable path while shortening the second transmissioncable path.
 15. An apparatus, comprising: a shaft comprising a distalend portion and a proximal end portion; a wrist mechanism coupled to thedistal end portion of the shaft, actuation of the wrist mechanismproducing movement of a distal portion of the wrist mechanism relativeto a proximal portion of the wrist mechanism; an end effector coupled tothe distal portion of the wrist mechanism, actuation of the end effectorproducing movement of the end effector relative to the distal portion ofthe wrist mechanism; a first cable comprising a first end and a secondend, the first end of the first cable routed to the distal end portionof the shaft; a second cable comprising a first end and a second end,the first end of the second cable routed to the distal end portion ofthe shaft; and a transmission coupled to a portion of the shaft, thetransmission comprising an input connection, an input shaft, a firsttransmission cable path, a second transmission cable path, and anadjustment mechanism, the input connection being configured to be drivenby an actuator of a control mechanism, the input shaft operativelycoupled to a second end of the first cable and configured to move thesecond end of the first cable, the first cable being routed through thefirst transmission cable path within the transmission between the inputshaft and the shaft, the adjustment mechanism having a first arm portionwith a first guide mounted thereon, the first guide being in contactwith a portion of the first cable, the first arm portion being movablesuch that movement of the first guide changes a first transmission cablepath length, and the adjustment mechanism having a second arm portionwith a second guide mounted thereon, the second guide being in contactwith a portion of the second cable, the second arm portion being movablesuch that movement of the second guide changes a second transmissioncable path length.
 16. The apparatus of claim 15, wherein the firstguide and the second guide are operatively linked such that movement ofthe first guide results in movement of the second guide.
 17. Theapparatus of claim 15, wherein in response to the first arm portionrotating between a first arm first position and a first arm secondposition, the first guide is moved closer to the input connection in thefirst arm first position than in the first arm second position.
 18. Theapparatus of claim 17, wherein in response to the second arm portionrotating between a second arm first position and a second arm secondposition, the second guide is moved closer to the input connection inthe second arm first position than in the second arm second position.19. The apparatus of claim 15, wherein the first guide comprises a firstpulley and the second guide comprises a second pulley.
 20. The apparatusof claim 15, wherein movement of the first guide in a first directionincreases the first transmission cable path length while shortening thesecond transmission cable path length, and moving the first guide in asecond direction shortens the first transmission cable path length whilelengthening the second transmission cable path length.